What is diarrhea?

Diarrhea is bowel movements (stool) that are loose and watery. Diarrhea is a common condition and is usually not serious. Many people will have diarrhea once or twice a year. It usually lasts two to three days and can be treated with over-the-counter medicines.

Some cases need medical attention because diarrhea can quickly eliminate water and salts that the body needs to function. Very young, very old, and very sick people may have difficulty replacing these lost fluids. Diarrhea that lasts for several weeks or contains blood may mean that you have a serious illness. In these cases, you should contact your healthcare provider.

Can diarrhea harm your health?

Persistent diarrhea causes the body to lose large amounts of water and nutrients. If you have diarrhea more than three times a day and you are not drinking enough fluids, you could become dehydrated. Dehydration is the loss of water from body tissues, which disturbs the balance of essential substances in your body. Dehydration can cause serious complications if it is not treated.

Tell your healthcare provider if you have persistent diarrhea and have any of the following signs of dehydration:

  • Dark urine
  • Small amount of urine
  • Rapid heart rate
  • Headaches
  • Flushed, dry skin
  • Irritability
  • Confusion

What causes diarrhea?

The most common cause of diarrhea is a virus that infects the bowel. The infection usually lasts for two days and is sometimes called "intestinal flu." Diarrhea also may be caused by:

  • Infection by bacteria
  • Infections by other organisms
  • Eating foods that upset the digestive system
  • Allergies to certain foods
  • Medications
  • Radiation therapy
  • Malabsorption of food (poor absorption)

Diarrhea also may occur after constipation, especially for people who have irritable bowel syndrome.

What are the symptoms of diarrhea?

The symptoms of mild diarrhea include:

  • Bloating or cramps in the abdomen
  • Thin or loose stools
  • Watery stool
  • A strong need to have a bowel movement
  • In some cases, nausea (upset stomach) and vomiting

In addition to the above symptoms, symptoms of severe diarrhea include:

  • Blood, mucus, or undigested food in the stool
  • Weight loss or dehydration (lack of water)
  • Fever
  • Severe pain

Severe diarrhea may be a sign of a more serious illness; if you have these symptoms, you should call your doctor. Contact your healthcare provider if the diarrhea continues for a long time, or if you have a fever that lasts more than 24 hours. Also, see your doctor right away if vomiting prevents you from drinking liquids to replace lost fluids.